Question

Determine sen x, sabendo que 0 < x < π/2 e cos x = 4/5. *
a) -3/5
b) -4/5
c) 3/5
d) 4/5

Answer 1

$\large\boxed{\begin{array}{l}\sf cos(x)=\dfrac{4}{5}\implies cos^2(x)=\dfrac{16}{25}\\\\\sf sen^2(x)=\dfrac{25}{25}-\dfrac{16}{25}=\dfrac{9}{25}\\\\\sf sen(x)=\sqrt{\dfrac{9}{25}}\\\\\sf sen(x)=\dfrac{3}{5}\\\huge\boxed{\boxed{\boxed{\boxed{\sf\maltese~alternativa~c}}}} \end{array}}$